The present invention relates to a surge arrester having a reinforced housing. More specifically, the present invention relates to an arrester housing that includes substantially rigid support members that surround and support varistor elements of the arrester and provide mechanical strength to the arrester housing.
A surge arrester is a protective device for power distribution systems. In particular, a surge arrester directs any over current in the system to ground. Conventional surge arresters include a current path to ground through resistance or varistor elements that dissipate the surge in current without damage to the utility line equipment.
Conventional surge arresters have an outer housing made of an insulative material such as porcelain or a polymer resin, and encloses a compressed stacked of varistor elements, such as metal oxide varistor (MOV) blocks. The varistor elements are typically wrapped by a weave casing or are surrounded by structural members. The varistor elements are electrically connected between the line current of the system and ground. The structural members surrounding varistor elements of a conventional arrester are usually not attached to the varistor elements and therefore must be attached to another part of the arrester housing, such as the end caps or end terminals. Assembly time and difficulty are increased due to the additional steps in attaching the structural members to the arrester housing. Moreover, separate fasteners are required to attach the structural members to the arrester housing.
During a catastrophic failure, an electrical arc is formed within the arrester housing triggering the generation of gases by the varistor elements and typically resulting in an explosion of the arrester due to the pressure of the internal gases. The weave casing or structural members of conventional arresters typically fail to control the internal gases and the exploding varistor elements, and the bursting arrester tends to shatter and throw parts resulting in property damage.
Examples of conventional surge arresters include U.S. Pat. No. 4,352,140 to Axelsson et al; U.S. Pat. No. 4,851,955 to Doone et al.; U.S. Pat. No. 4,989,115 to Bourdages et al.; U.S. Pat. No. 5,363,266 to Wiseman et al.; U.S. Pat. No. 5,402,100 to Urbanek et al.; and U.S. Pat. No. 6,185,813 to Donnola.
Accordingly, an object of the present invention is to provide a surge arrester with a housing that substantially prevents explosion of the arrester housing during a catastrophic failure.
Another object of the invention is to provide a surge arrester with a housing that includes substantially rigid support members located within the housing providing reinforcement thereto.
Yet another object of the invention is to provide a surge arrester with support members that both reinforce the arrester housing and support the varistor elements of the arrester.
Still another object of the invention is to provide a surge arrester with a reinforced housing that is easily assembled without the need for additional fasteners.
The foregoing objects are basically attained by an arrester including a housing having an inner bore, and a substantially cylindrical varistor body received in the inner bore of the housing. The varistor body is formed of at least one varistor element having a lateral outer surface and a length defined between first and second ends of the varistor body, and a first mating element extending outwardly from the outer surface and along substantially the entire length of said body. A substantially rigid first support member is received in the inner bore and is disposed on the outer surface of the body. The first support member has a first mating surface that corresponds to and engages the first mating element of the body, thereby coupling the body and the first support member.
The foregoing objects are also attained by a method of making an arrester by mating a plurality of substantially rigid support members with a substantially cylindrical mold core so that first mating elements of the mold core engage corresponding second mating elements, respectively, of the support members. The method also includes molding a housing around the support members and the mold core and removing the mold core from the housing, thereby forming an inner bore of the housing. The method additionally includes inserting a substantially cylindrical varistor body formed of a plurality of varistor elements into the inner bore of housing so that third mating elements of the body engage the second mating elements, respectively.
By fashioning the arrester in this manner, the arrester housing is reinforced thereby preventing shattering of the arrester during failure, and the assembly of the arrester is simplified.
Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with annexed drawings, discloses a preferred embodiment of the present invention.